As a general matter, gerrymandering is less important to the declining competitiveness of congressional elections than is generally believed. State boundaries haven't changed at all in decades, but Senate races are becoming less competitive, too. The main problem here is that elections are becoming increasingly expensive.

Thanks to a variety of studies, this is seeming much less true than we once thought. It's true that most incumbents outraise their opponents, but that advantage is no longer thought of as causal to their triumph, it's more correlated to the simple fact that they're incumbents with more ties to party machinery and more votes for lobbyists to buy. Indeed, the much stronger factor is polarization -- you can have all the money you want, but if you're from the wrong party, you might as well put it to good use remodeling your kitchen. And since party polarization has been rapidly increasing over the past few decades, that's probably a better explanation for why Senate races are becoming less competitive.

In any case, these things are multicausal -- it could be that an increasingly apathetic electorate has made name recognition and familiarity more important than they used to be. Could be that folks don't trust the news anymore and aren't listening to media recommendations to oust incumbents. I don't know. But for now, money doesn't seem a good candidate and party polarization, by and large, does. Some interesting paragraphs on this from an old Roll Call article follow the jump: